Signal acquisition system for surface acoustic wave magnetic sensor

Abstract

The invention discloses a signal acquisition system for a surface acoustic wave magnetic sensor. The signal acquisition system comprises a first oscillating circuit, a second oscillating circuit, a mixer circuit, an amplifying and shaping circuit and a single-chip microcomputer frequency measuring circuit, the first input end of the mixer circuit is connected with the first oscillating circuit, and the second input end of the mixer circuit 3 is connected with the second oscillating circuit; the amplifying and shaping circuit is connected with the signal output end IF of the frequency mixing circuit; the frequency measuring circuit is mainly connected with the signal output end of the amplifying and shaping circuit; the first oscillating circuit and the second oscillating circuit are used for outputting SAW sensor measuring frequency signals. According to the invention, a Pierce type oscillating circuit is adopted, and a SAW sensor is easy to perform self-excited oscillating to output asinusoidal signal with a specific frequency. Furthermore, the magnetic field intensity can be measured through a single difference value, namely the change of the signal frequency of a measuring branch. The precision is high, the detection range is wide, and no test blind area exists.

Description

technical field [0001] The invention belongs to the technical field of signal acquisition systems, and particularly relates to a signal acquisition system for a surface acoustic wave magnetic sensor. Background technique [0002] Surface Acoustic Wave (SAW) is an elastic wave propagating along the surface of a solid. Through the interdigital transducer structure, surface acoustic waves can be excited and detected on the surface of piezoelectric materials. The magnetostrictive film (FeCo, NiFe, Metglas, etc.) is introduced into the interdigital transducer. Under the action of the external magnetic field, the Young's modulus of the magnetostrictive material changes, and the surface acoustic wave velocity also changes, so as to achieve detection. The purpose of the weak magnetic field. The magnetic field sensitivity of the reported high-Q SAW resonator can reach more than 150Hz / μT, and the detection limit can reach nT / Hz 1 / 2 magnitude. Compared with other magnetic field sen...

AI Technical Summary

Problems solved by technology

In this method, due to fluctuations in the frequency of the DDS excitation signal, small changes in the SAW resonance frequency are sometimes difficult to detect, that is, there is a blind area for sensing signal detection

Although the phase / amplitude detection method does not involve frequency measurement, due to the limited output frequency range of the signal generator, it is difficult for high-frequency SAW devices to vibrate, and the range of detection signals is limited

Moreover, the circuit structure of this method is complicated, which is not conducive to the detection of the sensor array, and it is difficult to apply in practice.

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